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GeographyMediumAsked in: NDA · NDA-II 2017, GAT

Consider the following characteristics of a tropical cyclone : 1. A warm sea temperature of > 26°C 2. High relative humidity of atmosphere at a height of > 700 m 3. Atmospheric instability The above mentioned characteristics are associated with which one of the following cycles of its development ?

  1. A.Formation and initial stage
  2. B.Modification stage
  3. C.Full maturity
  4. D.Decay

Correct answer

A. Formation and initial stage

Explanation

The correct answer is A, Formation and initial stage. Warm sea water, moist air and an unstable atmosphere are the conditions a tropical cyclone needs in order to be born.

A tropical cyclone draws its energy from the latent heat released when water vapour condenses. So it can form only over seas warmer than about 26–27°C, where plenty of moist air rises. High humidity in the lower and middle atmosphere feeds the clouds, and atmospheric instability lets the warm air rise rapidly into tall cumulonimbus towers. A Coriolis force strong enough to start rotation and weak vertical wind shear are also needed, which is why cyclones do not form right on the equator.

B is wrong: in the modification stage the storm is already formed and changes shape and track. C is wrong: at full maturity the storm has a clear eye and its strongest winds; the listed conditions only describe how it begins. D is wrong: a cyclone decays when it moves over land or cold water and loses its supply of warm, moist air.

Exam tip: Cyclone birth needs sea above 26°C, high humidity, instability and the Coriolis force; it dies over land.

Practice Questions

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Q3.GeographyAsked in: CDS · CDS-II 2025, GKHard

Identify the climate type based on the given below characteristics : 1. The annual precipitation is low and is around 15 cm. 2. The development of pronounced winter anticyclones and their weakening in summer sets in monsoon-like reversal of wind in this region. 3. Polewards, summer temperatures are low. Select the answer from the options given below:

  1. A.Subtropical steppe
  2. B.Humid sub-tropical climate
  3. C.Cold climate with dry winters
  4. D.Tundra climate
Show answer
Correct answer: C. Cold climate with dry winters

All three features match the Dw type of Köppen's scheme, found mainly over north-eastern Asia. In the Dw climate, an intense high-pressure system, the Siberian anticyclone, builds up over the frozen land in winter and sends cold, dry winds outward.

Q4.GeographyAsked in: CDS · CDS-II 2025, GKMedium

Which of the following statements with reference to lines of latitudes is/are correct ? 1. The distance between two successive latitudes changes slightly from the equator to the poles. 2. If parallels of latitude are drawn at an interval of one degree, the total number of parallels thus drawn, including the equator, will be 179. Select the answer using the code given below :

  1. A.1 only
  2. B.2 only
  3. C.Both 1 and 2
  4. D.Neither 1 nor 2
Show answer
Correct answer: C. Both 1 and 2

The Earth is slightly flattened at the poles, and the poles themselves are points, not lines. Because the Earth is an oblate spheroid, a degree of latitude is a little shorter at the equator, about 110.6 km, than near the poles, about 111.7 km.